Hey boys. Been a minute since I've been on the old forum.
I'm about to build a L20B with a L series 5 speed in my 1200 ute.

My question is does anyone have advice on piston choice etc?
People have suggested the 280zx flattop pistons?
Any advice on head work? Valve grinds, porting etc?
I'm going to be running a comp cam, isky valve springs and retainers, changing over to efi itb set up, LS coil packs, and using a haltech 550 ecu.
Keen to hear any feedback! I have never built a l20b. So find the best way to go about.
Thanks guys
Tommy

Good question

* For best-bang-for-your-buck, go with whatever pistons and cam comes with your L20B. The torque alone will make the 1200 move, all without needing to rev that four-cylinder higher than the stock 7,000 rpm

* For most HP, go with a higher RPM cam grind, and steep rear diff gears. Come to think of it, the 1200 ute already comes a 4.11 diff, good for revving up and make to motor sing

* For best fuel economy, go with flat-top pistons and a lower gear ratio, like the 3.454 that's available for the H165 diff in the ute

The difference between 8:5 dished pistons and 10:1 flat-top pistons is like 5% more power. So instead of 120kw, you could get like 126kw. Or conversely get more kms per litre

L20B in 1200

Thanks for the info my friend!

So not worth overdoing the pistons as it won't do much at all?

I am going to strip the motor, deck the block and head. And refresh everything before I put it in the car. Just for peace if mind. I like building things right.
So you think where I'm going with my build is sufficient?

yeah, new gaskets and inspection/measurements are a good idea


Changing to flat-top pistons will up the compression ratio (good for maybe 6kw) but if the L20B head is an open type it may not help the fuel economy much

L20B four-cylinder made 70kw in stock spec 1981 910 Bluebird. That's compared to 50kw from the 1200 ute engine. So even without higher-rev cam and better pistons it makes 40% more power, right out of the box. Better yet is the 152nm torque, compared to a measly 95nm out of the 1200 motor. This is why it can easily trundle along with low-geared diffs, saving fuel while still giving better acceleration

Regarding the lowly L16 (same power as L20B, but far less torque), unfamilia said:Quote:
Of course, for best acceleration, use the stock diff and shift more often (as it will rev faster). With a five-speed gearbox you'll still get good fuel economy on the highway without the slower diff


So better pistons and cams will pay off in faster acceleration. But is it worth $2500 for a bit more power? Or just swap in a re-conditioned L20B for maybe $1000 and start driving?

If you fit tubular extractors and open air filters it will sound every bit of the "built" version


Ultimately, going all out with 8500 RPM cam, a 4.62:1 diff, ported cylinder head and dual-weber 45s would be cool, and could make 200kw/150hp. Rev it up and shift! Only downside is time and money. BTW, all these power figures are "at the engine" (engine dyno) the same way that the car manufacturers rate them. "At the wheels" (chassis dyno) figures will be lower